Vacuum-tube circuits.



H. W. NICHOLS.

VACUUM TUBE CIRCUITS. APPLICATION FILED DEC.28. 19m

1 $325,879 Patenfied Dec. 23, 1919..

Mwmiar: Ham/d W. Mic/vols.

STATES PATENT OFFICE. A

onn w. Monet's, or MAPLEWOOD, NEW J RSEY, nssrenon r0 wnsrnnn ELnc'rnIo CUMPANY, INCORPORATED, QF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

vacuum-roan cmcurrs.

Application flledDecember 28, 1916. Serial No, 139,818.

To all whom it may concern:

Be it known that I, .HAROLD WILLIAM Nrcnons, a citizen of the United States, re

sidin' at Maplewood, in the county of Essex and %tate of New Jersey, have lnvented certain new and useful Improvements 1n Vacuum-Tube Circuits, of which the following is a full, clear, concise, and exact description. 0

This invention relates to vacuum tube c1rcuits.

Ttsiobject is to prevent any undeslred capacit efiects between the electrodes 1nclosed in a vacuum tube.

Tn vacuum tubes of the audion type, there are, in general, three electrodes, namely, the filament, the plate and the grid. Tn view of their relative positions, there will be a cer-.

tain amount of electrostatic capacity between these members. en a circuit containing such a tube is subjected. to an alternatin voltage, there will be a flow of current tiirough certain branches of the c rcuit due to this capacity efl'ecfi For the ordinary vacuum tube, these capacities are exceedingly small, and the .displacement currents resulting therefrom, at moderate frequencies, are negligibly small. If the frequencies used in the circultbecome high, say of the order of half a million, the

capacity or displacement currents may be appreciable. I

lit has been found that such displacement currents are deleterious in that they decrease the efficiency of operation ,of the vacuum tube and may, under certain conditions, en-

tirely block the action of the tube. This is partlcularly true as to the displacement current which may flow between the grid and r the potential difference between the filament and grid to materially aifect the output current.

The object of this invention is to prevent.

the flow of such current, and theobject is attained by. addin certain elements to the circuit whereby t e capacity between the plate and grid becomes a ortion of a circuit which is antiresonant or that frequency Specification of Letters Patent.

applied to a vacuum tube amplifier of'the Patented Dec. 2 3, 19 19.

which is being used in the circuit. V By the term anti-resonant is meant a circuit whlch ofiershigh impedance to the passage of currents of the same frequency as that for which the circuit is tuned, but which provides a low impedance path for currents of other frequencies differing from the frequency for which the anti-resonant circuit is tuned.

With sufiiciently high frequencies, the capacity or displacement current bet-Ween grid and filament may also become large enough to be harmful and an;arrangement similar to that described above may be resorted to in order to overcome such harmful effects.

The invention will be better understood by reference to the followin specification and accompanying drawings, in which Fi re 1 shows one embodiment of this invention as audion type.

Fig. 2 illustrates the inventionas applied.

to a plurality of audion amplifiers inparallel.

Referring to Fig. 1 of the drawing, 4 is a.

vacuum tube of the audion type containing a'filament 5, a grid 6 and a plate 7. The

input circuit 8 receives electric oscillations from the generator or source of electric. oscillations 9 by means of the transformer 10. These oscillations appear in amplified form in the output circuit 13 and are impressed by means of transformer 14:" on any desired circuit 15, which has a capacity'lfi and a resistance 17. lit the oscillations are of the order of one thousand cycles per second, the capacity efl'ects, due to the electrodes are negligible, but if they are of the .order of a millioncycles per second, there willlbe an appreciable capacity efi'ect between thegrid 6 and plate 7, and, consequently, a current flow between the input and output circuits. Such being the case, the output circuit would react upon the input circuit and would either materially change the character of the. oscillations impressed upon the input circuit or cause them to cease entirely.

To avoid this reaction, I gopose t'o lnsert betweenthe points A and an inductance 21';- which,

together with the capacity efiect between the ,I-grid and plate, is of suchavalue as to form a circuit 22 that is sharply tuned to the generator frequency. If such is the case, the

impedance from point A to point B is infinite in value .so that no "current can flow between said points, and circuit 22 becomes anti-resonant to the generator fre uency.

1 The capacity is a large capacity a ded to "termined only by the amount of capacity the circuit to revent a flow of direct current between ,t einput and output circuits from either the. in ut battery or the output battery 26. n account of its size the capacity 20 may therefore be neglected m the tuning of circuit 22 that is, for a given frequency the value of inductance 21 18 debetween the grid and the plate.

In the case of high frequency oscillations, the capacity effect across the grid and filament may, as mentioned above, be sufiiclent' to allow an appreciable amount of current to flow in the input circuit 8. This would permit the input circuit to react on the oscilla tion generator, which reaction should be avoided for reasons previously mentioned, and wouldalso become adiminution of the efi'ective voltage impressed across the input terminals. In order 'to obtain the condition that the efi'ect of the capacity between theinput electrodes shall be inappreclable, .I

- propose to. connect an inductance 24 across the input terminals of such a value that, taken with the efl'ective capacity between the grid and filament, it forms a circuit antiresonant forthe given frequency of the enerator, thereby making the impedance 0 the input circuit infinite in value so that no current can fiow between the points C and D.

Although the capacity efi'ects maybecome appreciable in the case of a single tube connected as shown in Fig. 1, the efiect becomes much more .marked when a plurality of tubes are connected in parallel. Such a ci-rcuit is shown in Fig. 2 where a plurality of same purpose as condenser 20 of Fig. 1, and, in general, is so large as to have no. appreciable efi'ect on the impedance of the.c 1r-' cuit. Inductance 38, together with. the total capacity between the various filaments 31 and grids 32, is of such a. value as, to' form another circuit anti-resonant to the frequency of the oscilliations in the system, thereby reducing to zero the undesired current flow in the secondary of transformer 10, and thus preventing any reaction effects,

as well as loss of efi'ective voltage.

It is obvious that this invention, as set char e tube with two or more electrodes in -whic it is desired to prevent the effects due to thecapacity or displacement currentbetween any two electrodes.

What 1s claimed is:

1. A source of oscillations of an ultra audio frequency, a vacuum tube device havin electrodes, means for impressing said oscil ations upon said device, a circuit containing said electrodes, said circuit offering a path of high impedance to said oscillations while bein lower in value for otherv freuencies, t ereby. preventing said device rom reacting upon the source of oscillations.

2. A source of oscillations, a vacuum tube device having electrodes, means for impressing said oscillations upon said device, means for preventing said device from reacting upon said source, said means comprising a plurality of circuits each anti-resonant to the frequency of the oscillations of said source associated with said electrodes.

3. A vacuum tube device having an input and an output circuit, a source of oscillations of an ultra audio fre quency,means for impressing said oscillations upon said device, means for preventing thereaction of said output circuit upon said input circuit for said frequency, sald means comprising a circuit anti-resonant to said frequency.

1. A vacuum tube device havin input and output circuits, a source of oscillations of an ultra audio frequency for said input circuit, means for preventing a flow of current between said .circuits, said means comprising a circuit sharply tuned to said oscillations.

5. A vacuum tube device having input and output circuits, a source of oscillations of an ultra audio frequency and means comprising an impedance, high in value for said frequency' and low in value for others, interhnked between sald' circuits, whereby any appreciable flow of current between said circuits of said frequenc is prevented.

' 6. A vacuum tube evice having an input electrode and an output electrode, a source of oscillations of an ultra audio frequency,

input and output circuits, means comprising an inductance in a circuit shunted across said electrodes for providing a high impedance for said frequency between said input and output-circuits.

7. A- vacuum tube device having an input electrode and an output electrode, input and forth 1n the appended claims, may be apoutput circuits, a source of electric oscillaneaaevo tions of an ultrayaudio frequency for said for impressing said oscillations upon said input circuit, means for making the impedance of said input circuit high in value, said means comprising a circuit including said electrodes, said last mentioned circuit being anti-resonant to said frequency.

9. A vacuum tube device having input electrodes, an input circuit, a source of oscillations of an ultra audio frequency, means for impressing said oscillations upon said input circuit, giving rise to a capacity effect between said lnput electrodes, an inductance in a circuit shunted across said electrodes, said inductance and capacity forming a circuit antiresonant to saidoscillations, thereby preventing said input circuit from reacting upon said source of oscillations.

l0 A vacuum tube device having input and output electrodes, and an input circuit and an output circuit, a source of oscillations of an ultra-audio frequency, an anti-resonant circuit for said oscillations having a portion thereof shunted around said electrodes, thereby preventing said output circuit from reacting upon said source. 7

ill. The combination with an evacuated vessel containing a cathode, an auxiliary electrode and an anode, of a source of oscillations of an ultra audio frequency and means for neutralizing the capacity effect at said frequency between said auuiliary elec trode and said anode.

it. The combination with an evacuated vessel containing a cathode, an auxiliary electrode and an anode, of a source of oscillations of an ultra audio frequency and a localcircuit including said auxiliary electrode and said anode for neutralizing the capacity effect at said frequency between said auxil iary eiectrode and said anode I a it. The combination with an evacuated vessel containing a cathode, an anode and an auxiliary electrode, of acircuit'over which impulses are transmitted to said electrodes and an auxiliary circuit comprising an inductance and a condenser incircuit' with bill said auxiliary electrode and said anode for neutralizing the capacity between said auxiliary electrode and said anode.

1a The combination with an evacuated vessel having a plurality of electrodes, of a,

source of oscillations of an ultra audio frequency and means comprising unantiresonant circuit for neutralizing the capacity effect of'said frequency between two of-said electrodes.

15. The combination ofan evacuated vessel having'a plurality of-electrodes, of a source of oscillations of an ultra audio frequency and means comprising a circuit antiresonant to said frequency for neutralizing tne efi'ect of the capacity between two of the electrodes for said frequency,

16. The combination with a vacuum tube device havingelectrodes of asource of oscillations of an ultra-audio frequency and amplifier containing a cathode, an anode and aninductance in a branch of a circuit antiresonant to said frequency shunted around said electrodes for neutralizing the edect atsaid frequency of the capacity between two of said electrodes.

l7. lhe combination with a vacuum tube a grid, of a source of oscillations of an ultra audio frequency and a local circuit contalning'said grid and anode, sald clrcult ha ing high impedance for currents'of said free? quency'while having a low im edance for currents of frequencies considera ly removed from said frequency, v

18. 'llhe combination. with an evacuated vessel containing a cathode. an anode, and an auxiliary electrode, of 'a circuit over which impulses are transmitted to said electrodes and an auxiliary circuit comprising an inductance and a condenser in series with said auxiliary electrode and said anode;

19. A vacuum tube device having input and output electrodes and an input circuit and an output circuit, a source of oscillations of an ultra-audio frequency, and an antiresonant circuit for said oscillations com prising a plurality of branches in one of which are said electrodes, thereby preventing said outgoing-circuit from reacting upen said source. 4 r in witness whereof, l hereunto subscribe my name this fifth day of December, D,

nauonn vv. sinuous,

lilt 

